The present invention relates to a method for producing components for separating nozzle elements for separating gaseous mixtures, particularly isotope mixtures, in which the components are provided with perforations serving to form gas supply channels, separating chambers and gas discharge channels.
According to gas-kinetic scaling relations, the gas pressure value producing a minimum specific energy consumption, or optimum operating pressure value, is inversely proportional to the characteristic dimensions of the separating nozzle structure, as described in Chemie Ing. Technik [Chemical Engineering Art] 39(1967), at page 4. Since the expenditures for the compressors, pipelines and valves required for this process decrease considerably with increasing gas pressure, it is desirable to make the separating nozzle structure as small as possible.Thus, a separating slit for withdrawing the heavy fraction having a width of no more than about 10.mu. here corresponds to an inlet pressure of, e.g., 0.5 bar.
It is known to produce separating nozzles with particularly small characteristic dimensions by assembling them from a stack of mutually aligned foils each provided with a plurality of perforations formed to define the gas inlet channel, the curved nozzle, separator channels and discharge channels, as disclosed in German Auslegeschrift [Published patent application] No. 2,009,265. The perforations are preferably etched into the foils.
In the etch shaping process accepted in practice, and described, for example, in Naturwissenschaften [Natural Sciences] 63 (1976) at pages 408-409, the structural density, i.e. number of nozzles per unit area, on the foils can be increased by reducing all nozzle dimensions. However, this requires that the foil thickness by reduced simultaneously in order to retain the relative etching accuracy. Experience has shown that the optimum ratio of foil thickness to narrowest perforation width, or aspect ratio, for an etch shaping process is of the order of magnitude of unity.
With the desired inlet pressure of .gtoreq.0.5 bar, the optimum foil thickness is thus 10.mu. or less. Processing and manipulating such extremely thin foils is not easy and requires considerable manufacturing expertise. The small aspect ratio of the foils produced according to such etch shaping process, moreover, has a substantial adverse influence, manifested by stacking errors, on the output of the separating nozzle elements. This occurs because the small foil thickness dictated by the limited aspect ratio value creates the probability of large stacking errors, or offsets, per unit of slit length. There thus exists the danger that the above-mentioned advantage offered by an increase in the gas pressure would be accompanied by higher manufacturing costs and/or a reduction in the output of the separating nozzle elements.